feat: v2.5.5 — AI Router renamed AI Proxy, reload onto new builds, update no longer spins

AI Proxy (was AI Router):
- server/lib/ai-proxies.js, proxy-apply.js, routes/ai-proxies.js mounted at
  /api/ai-proxies and the old /api/ai-routers; `router` still accepted on the
  start routes; profiles move to <CLAUDE_HOME>/agenthub-proxies/
- dashboard_runs.router renamed in place to proxy: an older build on the same
  DB fails on that column, so dev and prod sharing one DB update together
- a proxy's baseUrl stored as its root (a typed /v1 made /v1/v1/messages);
  Test probes Claude /v1/messages and Codex /v1/responses
- Settings → AI Proxy (/settings/ai-router redirects), ProxyPicker

Updates:
- every tab reloads onto the new UI build when its WebSocket reconnects to a
  server of another version (lib/newBuildReload.ts, once per version)
- Update now stops waiting on a plugin chain that failed or pulled nothing
  (the old server never goes down), and reloads as soon as a new version answers

Also:
- a pane whose command exits at once says so (EPANEEXITED) instead of
  "Command failed: tmux set-option … mouse on"
- the pane drag preview draws where the pane actually lands

server/README.md

@@ -701,7 +701,7 @@ Because sync runs non-interactively (`ssh -o BatchMode=yes`), the connection mus
 | `GET`  | `/api/settings/claude-home`    | `{claude_home, env_owned}` — `env_owned` when the real environment or the checkout's `.env` set `CLAUDE_HOME` (a saved value is overridden at the next start) |
 | `PUT`  | `/api/settings/claude-home`    | `{path}` → validate, apply, persist to AgentHub's settings file. 400 `EBADHOME` (is or contains the OS home) / `INVALID_PATH`, 500 `ESAVE`, 403 `EBADORIGIN` (`sameOriginGuard`) |
 | `GET`  | `/api/settings/codex-home`     | `{codex_home, env_owned}` |
-| `PUT`  | `/api/settings/codex-home`     | Same checks as `claude-home`; a session's AI Router layer is written into the current home at its spawn, so nothing is re-written here |
+| `PUT`  | `/api/settings/codex-home`     | Same checks as `claude-home`; a session's AI Proxy layer is written into the current home at its spawn, so nothing is re-written here |
 | `GET`  | `/api/settings/codex-hooks`    | Status of AgentHub's hooks in `$CODEX_HOME/hooks.json` (installed, per-event, Codex's trust as read from `config.toml`) |
 | `POST` | `/api/settings/codex-hooks`    | Install or reinstall them (`sameOriginGuard`). 400 `EBADJSON` / `EUNSUPPORTED` / `EFOREIGN` (the forwarder path holds a file that is not AgentHub's) |
 | `DELETE` | `/api/settings/codex-hooks`  | Remove AgentHub's hooks only (`sameOriginGuard`); a foreign forwarder is left alone |